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Antiquated Sewers Get Modern Makeover

30 May 2006

Nineteenth Century sewers under the City of Des Moines have been updated with new thermoset composite liners installed by Visu-Sewer Clean & Seal.

To ensure minimal disruption to the bustling Iowa state capital, Visu-Sewer used cured-in-place pipe (CIPP) technology. To ensure long-term durability, the new liners are made with Vipel® L704-FAH resin, a proven high molecular weight isophthalic polyester engineered by AOC for CIPP use.

The new project rehabilitated more than 12,000 feet (3650 meters) of brick sewer lines ranging in diameter from 18 to 60 inches (46 to 152 centimeters). Most of the original combined storm and sanitary sewer lines is estimated to be 80 to 100 years old, and several sections under the downtown district were most likely installed in late 1800s.

“The brick itself has performed well,” comments City of Des Moines Project Engineer Jeff Hansen, “but the mortar is failing the test of time. To repair the sewers, we chose CIPP over ‘sliplining’ a thermoplastic liner inside the old pipe. Compared to CIPP, sliplining would have left us with less flow capacity and would have caused significantly more surface disruption.”

Hansen adds: “With sliplining, we would need to dig more openings to be able to install the liner through the many curves in the system. With CIPP, Visu-Sewer was able to install most of the new liner through existing manholes.”

Visu-Sewer uses National Liner CIPP technology licensed from National EnviroTech Group, LLC, Houston, Texas. National Liner technology calls for saturating a non-woven polyester felt liner with a corrosion-resistant thermoset resin, then inserting the liner into the pipe in need of repair. Under pressure, the felt liner is expanded against the interior of the host pipe. Under heat, the liquid resin cures into a crosslinked solid that encapsulates the felt to produce a new smooth, continuous liner inside the old pipe.

Visu-Sewer Project Engineer Alex Rossebo Visu-Sewer says that crews benefited from the good processing characteristics of Vipel L704-FAH resin. “Wet-out with the Vipel resin was never an issue, regardless of location” he states. “Wet-out of liners up to 48 inches (122 centimeters) were performed at our facility in Pewaukee, Wisconsin. For the 60-inch (152 centimeter) liners, three over-the-hole wet-outs were performed on site next to the Des Moines River. The longest over-the-hole insertion was approximately 1000 feet (305 meters).”

The image shows the sewer under this narrow, tree-lined street of the city’s downtown transit mall was upgraded without causing surface disruption. “We would not want to dig this street up,” said City Project Engineer Jeff Hansen.